In the processing and packaging of semiconductor devices, wire bonding continues to be the primary method of providing electrical interconnection between two locations within a package (e.g., between a die pad of a semiconductor die and a lead of a leadframe). More specifically, using a wire bonder (also known as a wire bonding machine) wire loops are formed between respective locations to be electrically interconnected. Wire bonding machines may also be used to form conductive bumps (which bumps may, or may not, be used in connection with wire loops).
An exemplary conventional wire bonding sequence includes: (1) forming a free air ball on an end of a wire extending from a bonding tool; (2) forming a first bond on a die pad of a semiconductor die using the free air ball; (3) extending a length of wire in a desired shape between the die pad and a lead of a leadframe; (4) stitch bonding the wire to the lead of the leadframe; and (5) severing the wire. In forming the bonds between (a) the ends of the wire loop and (b) the bond site (e.g., a die pad, a lead, etc.) varying types of bonding energy may be used including, for example, ultrasonic energy, thermosonic energy, thermocompressive energy, amongst others.
U.S. Pat. No. 5,595,328 (titled “SELF ISOLATING ULTRASONIC TRANSDUCER”); U.S. Pat. No. 5,699,953 (titled “MULTI RESONANCE UNIBODY ULTRASONIC TRANSDUCER”); U.S. Pat. No. 5,884,834 (titled “MULTI-FREQUENCY ULTRASONIC WIRE BONDER AND METHOD”); and U.S. Pat. No. 7,137,543 (titled “INTEGRATED FLEXURE MOUNT SCHEME FOR DYNAMIC ISOLATION OF ULTRASONIC TRANSDUCERS”) relate to ultrasonic transducers and are herein incorporated by reference in their entirety. Ultrasonic bonding energy is typically applied using an ultrasonic transducer, where the bonding tool is attached to the transducer. The transducer typically includes a driver such as a stack of piezoelectric elements (e.g., piezoelectric crystals, piezoelectric ceramics, etc.). Electrical energy is applied to the driver, and converts the electrical energy to mechanical energy, thereby moving the bonding tool tip in a scrubbing motion. This scrubbing motion of the bonding tool tip is typically linear motion along the longitudinal axis of the transducer.
It would be desirable to provide improved transducers for use in connection with wire bonding machines, and improved methods of forming wire bonds using transducers.